Espresso coffee is roasted darker than ordinary coffee varieties to give it a more bitter taste. The ground coffee is put into a small canister and clamped on to the coffee machine. The machine then forces pressurized steam through the coffee grounds to produce an oily black liquid.

Espresso is significantly stronger than filter coffee, but is served in far smaller measures, meaning you need approximately a double espresso to match the amount of caffeine found in a normal-sized cup of filter coffee.